Tangential, a custom 'desktop', but I realised I could build a complete, stand-alone, network-render 'Box' for less than cost of significantly upgrading either of my now-ageing CAD-Tower's twin graphics cards. To put it politely, GPU card prices are scary...

'Box' has an an old 1GB Radeon 'office' GPU card driving a small VGA display, yet 32 GB and a Ryzen-7, so ~16 threads. Queue Manager happily uses 15¾ of them, 95~98% of CPU resource...

Turning the issue around, could you use either your old or next PC as a network-render resource ?

Per comments above, I'd shun Intel, got for the most AMD Ryzen threads I can afford. Even slightly under-clocked for thermal stability, each extra CPU thread totally trumps a few percent of clock-speed. 'Gotcha' is that AMD uses Ryzen-series die-space for either on-board GPU support or extra CPU cores...

Due Care, please ??